Foods That Fight Cancer

Beans (also known as legumes) include lentils, peas and many other bean varieties. (Soybeans also fall into this category, but their anti-cancer benefits are described in the soy section.) The active ingredients in beans that seem to have a role in cancer prevention include saponins, protease inhibitors and phytic acid. These phytochemicals appear to protect cells from the type of genetic damage that can lead to cancer. Beans are also rich in fiber, and diets high in fiber have been repeatedly linked to lower risk of colorectal, pancreatic and breast cancers.

In laboratory studies, saponins have shown the ability to inhibit the reproduction of cancer cells and slow the growth of tumors in several different tissues. Protease inhibitors have slowed the division of cancer cells and helped to prevent tumors from releasing substances called proteases that destroy nearby cells. Phytic acid has shown the ability to significantly slow the progression of tumors.

One recent case-control study involving 3,237 men of different ethnic backgrounds found that those subjects who consumed the most beans had a 38 percent lower risk of prostate cancer than subjects who consumed the least.

Berries are known as good sources of vitamin C and fiber and diets high in both of these substances have been consistently linked to lower cancer risk. But all berries, particularly strawberries and raspberries, are especially rich in a substance called ellagic acid, which has shown the ability to prevent cancers of the skin, bladder, lung, esophagus and breast in laboratory studies. This phytochemical seems to utilize several different anti-cancer methods at once: it acts as an antioxidant, it helps the body deactivate specific carcinogens, and it helps slow the reproduction of cancer cells.

Strawberries also contain a wide range of other flavonoids, each of which seems to employ a similarly wide array of anti-cancer strategies.  Blueberries contain a family of phenolic compounds called anthocyanosides, which seem to be among the most potent antioxidants yet discovered.

The cruciferous vegetables are broccoli, cauliflower, cabbage, Brussels sprouts, bok choy and kale. This family of vegetables contains many components that have been linked to lower cancer risk, including glucosinolates, crambene, indole-3-carbinol and, especially, isothiocyanates (which are derived from glucosinolates.)

Several laboratory studies have suggested that cruciferous vegetables help regulate a complex system of bodily enzymes that defend against cancer. Components of these vegetables have shown the ability to stop the growth of cancer cells in various cell, tissue and animal models, including tumors of the breast, endometrium, lung, colon, liver, colon and cervix.

Large human studies have associated diets high in cruciferous vegetables with lower risk for lung, stomach and colorectal cancers. The evidence from these studies, which compare the diets and disease rates of different populations, is less consistent for ovarian, endometrial and prostate cancers.

Studies that track the diets of many individuals over time, however, have found that diets high in cruciferous vegetables are associated with drastically lower rates of prostate and bladder cancer.

Clinical studies on the role of cruciferous vegetables in cancer development and recurrence are just beginning, but preliminary evidence suggests that diets high in these foods have beneficial effects on cellular metabolism that may translate into lower cancer risk.

Leafy green vegetables
such as spinach, kale, romaine lettuce, leaf lettuce, mustard greens, collard greens, chicory and Swiss chard are excellent sources of fiber, folate and a wide range of carotenoids such as lutein and zeaxanthin, along with saponins and flavonoids.

Carotenoids seem to help prevent cancer by acting as antioxidants that is, scouring potentially dangerous “free radicals” from the body before they can do harm.

Large scale studies have consistently linked low blood levels of carotenoids (indicative of a diet low in certain vegetables and fruits) with greater risk for cancer.

Researchers have found that carotenoids in dark green leafy vegetables can inhibit the growth of certain types of breast cancer cells, skin cancer cells, lung cancer and stomach cancer.

Results from several studies suggest that dietary folate is associated with lower risk of both colorectal adenomas (polyps which often progress into cancers) and colorectal cancer. Two large studies have suggested an association between increased dietary folate intake and reduced breast cancer risk in women who consume alcoholic beverages. In men, results from two studies indicate that diets high in leafy green vegetables and other sources of folate may reduce the risk of lung cancer, especially in smokers.

In the Iowa Women’s Health Study, women who ate the most green leafy vegetables were found to have less than half (44%) of the risk of ovarian cancer compared with subjects who ate the least amount of green leafy vegetables.

 

Flaxseed is available as flaxseed flour, flaxseed meal (which has the texture of cornmeal), flaxseed oil and whole flaxseeds. The whole seeds cannot be digested, so they provide no nutritional or health benefits unless they are ground.

Flaxseed is the best dietary source for substances called lignans. Lignans are classified as phytoestrogens (plant estrogens) because they seem to mimic the action of estrogen in the body. This behavior has been linked to reduced cancer risk. Flaxseed oil does not contain lignans (a group of phytochemicals studied for the anti-cancer abilities), but some manufacturers of flaxseed add them.

Flax is also high in one kind of omega-3 fatty acid. Omega-3 fatty acids are being studied for possible health benefits such as protecting against cancer and lowering cholesterol.

In several laboratory studies, flaxseed has inhibited the formation of colon, breast, skin and lung tumors. However, there is some indication that the anti-cancer effect of flaxseed varied widely depending upon the variety of flaxseed and its growing conditions.

A few laboratory studies involving rats have suggested that consumption of flaxseed during pregnancy and lactation produces hormonal changes in offspring that may impact their cancer development. These findings are preliminary and warrant further study.

In some short-term human studies, consumption of flaxseed has altered estrogen metabolism in ways that may indicate a protective effect against breast cancer. To date, the laboratory and clinical work on flaxseed and breast cancer has focused on estrogen-receptor negative breast cancers. The effect of flaxseed on estrogen-positive breast cancers has not been studied.

Currently, the evidence associating consumption of flaxseed with protection against prostate cancer is less consistent; some human studies indicate an increased risk, some a decreased risk, and still others find no association at all. In a recent clinical study, however, consumption of a low-fat diet combined with daily flaxseed for 5 weeks inhibited various aspects of prostate cancer biology in beneficial ways for a small group of prostate cancer patients.

Note: High amounts of flaxseed and flaxseed oil can reduce blood clotting and promote bleeding, and may interact with drugs that that have a similar effect, such as aspirin.

Both grapes and grape juice are rich sources of resveratrol, a specific type of natural plant chemical that belongs to a much larger group of plant chemicals called polyphenols. The skin of the grape contains the most resveratrol, and red and purple grapes contain significantly more resveratrol than green grapes. Grape jam and raisins contain much smaller amounts of this phytochemical. Wine also contains resveratrol, but alcohol has been consistently associated with increased risk for breast cancer and several other types of cancer, so wine is not a recommended source.

Several studies have found polyphenols in general and resveratrol in particular to possess potent antioxidant and anti-inflammatory properties. Resveratrol has been able to prevent the kind of damage known to trigger the cancer process in cell, tissue and animal models.

Resveratrol has been shown to slow the growth of cancer cells and inhibit the formation of tumors in lymph, liver, stomach and breast cells. Resveratrol has also triggered the death of leukemic and colon cancer tumors.

In one series of studies, resveratrol blocked the development of skin, breast and leukemia cancers at all three stages of the disease (initiation, promotion and progression.)

Since ancient times, tea has been used as both beverage and medicine. Both black and green teas contain numerous active ingredients, including polyphenols and flavonoids, which are potent antioxidants. One class of flavonoids called catechins have recently become the focus of widespread study for their anti-cancer potential.

Tea is the best source of catechins in the human diet, and green tea contains about three times the quantity of catechins found in black tea.

In laboratory studies, green tea has been shown to slow or completely prevent cancer development in colon, liver, breast and prostate cells. Other studies involving green tea have shown similar protective effects in tissues of the lung, skin and digestive tract.

Studies that track the diets of human subjects over several years particularly studies conducted in Asia, where green tea consumption is common have associated regular usage of green tea with lower risk for bladder, colon, stomach, pancreatic and esophageal cancers.

Very recently, human clinical studies have begun to explore consumption of green tea among cancer survivors. Preliminary results suggest that regular consumption (3 or more cups/day) of green tea is associated with reduced recurrence of early (Stage I) breast cancer. Evidence for prevention of Stage II and III breast cancer recurrence is less consistent.

Note: Very high amounts of green tea components (usually associated with overdosage of green tea supplements) have been shown to interact with drugs that affect blood clotting such as aspirin.

The soyfoods include tofu, soymilk, soybeans, soynuts, miso (soy paste), tempeh, soy burgers and soynut butter. Active ingredients in soy that appear to have anti-cancer effects are isoflavones (which have been the most studied), saponins, phenolic acids, phytic acid, phytosterols, and protein kinase inhibitors.

Laboratory studies involving soy have demonstrated a protective effect against cancer in the cells and tissues of the bladder, cervix, lung and stomach. Preliminary evidence suggests that diets high in soy may help make breast, cervical, ovarian, head and neck cancer cells more sensitive to the effects of chemotherapy and radiotherapy.

Soy appears to contain some components that resemble very weak forms of the body’s natural hormones. As a result, soy foods can mimic the actions of hormones under certain conditions and counteract these hormonal actions at other times. Because of such complexities, most of the studies that have investigated soy’s role in cancer development have dealt with hormone-related cancers such as those of the breast and prostate.

Soy has been shown to inhibit the growth of prostate cancer cells in a variety of laboratory conditions. In a large, human study, men who said they drank soymilk more than once per day for 20 years were found to have 70% lower prostate cancer risk than men who never drank soymilk. More recent human studies that have sought to determine the effect of soyfoods on hormones linked to prostate cancer have produced inconsistent evidence.

Soy has been associated with the inhibition of breast cancer cells in some, but not all, laboratory experiments. Diets rich soy have been shown to alter the metabolism of breast tissue in animal subjects in ways that may translate into added anti-cancer protection.

Several human and laboratory studies have suggested that consumption of soy early in life may help protect against breast cancer later in life. Results are less encouraging for a post-menopausal role. In fact, one recent analysis of available data concluded that soy consumption by adult women probably has little or no effect on either breast cancer risk or the survival of breast cancer patients.

The red or pink color of several fruits tomatoes, watermelon, papaya, pink guava and pink grapefruit comes chiefly from a carotenoid called lycopene. This potent antioxidant, together with a group of related compounds collectively called the “red family,” has displayed anti-cancer potential in a variety of studies. There is evidence that this potential is increased if tomatoes are consumed in a processed form that allows these natural compounds to be released and more easily absorbed, such as tomato sauce, tomato paste, and tomato juice.

Antioxidants can help protect against the kind of damage that gets cancer started, and the antioxidant nature of compounds within tomatoes has long been known. Recent evidence from laboratory studies suggest that tomatoes may help combat cancer in additional ways, at later stages of the process.

In the laboratory, tomato components have stopped the proliferation of several cancer cells types, including breast, lung, and endometrium. Tomatoes have attracted particular attention from prostate cancer researchers because lycopene and its related compounds tend to concentrate in tissues of the prostate. In animal models, consumption of tomato compounds has been linked to large decreases in prostate cancer risk.

In fact, studies that compare the diets and disease rates of different populations have repeatedly associated diets high in tomatoes with lower prostate cancer risk, as well as lower risk of stomach and pancreatic cancers.

One study that tracked the diets of a large group of men for six years found that those who ate the most tomato products (cooked tomatoes, tomato sauce, pizza and tomato juice) had a 35% lower risk of early prostate cancer and a 53% lower risk of advanced prostate cancer than men who ate the least of these foods.

A few, small clinical studies have investigated how tomato components (or tomato-rich diets) influence the prostate health of patients who have been treated for prostate cancer. Results are encouraging, but preliminary.

The term “whole grain” means that all three parts of the grain kernel (germ, bran and endosperm) are included. Refined grains usually have the bran and germ removed, leaving only the starchy endosperm. Brown rice is a whole grain, white rice is not. Other whole-grain foods include wheat breads, rolls, pasta and cereals; whole grain oat cereals such as oatmeal, popcorn, wild rice, tortilla and tortilla chips, corn, kasha (roasted buckwheat) and tabouleh (bulghur wheat.)

Whole grains are rich in fiber, vitamins, minerals and hundreds of phytochemicals. They contain several substances that have each been linked to lower cancer risk, including fiber (both soluble and insoluble), antioxidants, phenols, lignans, phytoestrogens and saponins.

Because of the wide range of anti-cancer ingredients they contain, diets high in whole grains may decrease cancer risk in general, and specifically the growth rate of breast cancer, via several simultaneous and synergistic methods.

When data from 40 recent studies on whole grains and cancer risk were combined and analyzed, the risk for cancer was reduced by 34% on average in people who ate large amounts of whole grains compared to those who ate small amounts.

Source: American Institute for Cancer Research